Method and apparatus for heat detection and control

ABSTRACT

A capillary protector is disclosed in which contained material, vaporizable at a temperature of interest, is maintained in exclusively liquid state when the protector is at a temperature below such preselected temperature. Methods for using such capillary protector and heating apparatus incorporating the same are also disclosed.

United States Patent 1191 1111 3,810,065 Welsh 1 May 7, 1974 METHOD AND APPARATUS FOR HEAT 3,163,045 12/1964 Kaveckas et a1 73/368.2 DETECTION A CONTROL 2,902,581 9/1959 Stiebel 219/513 1,684,530 9/1928 Bast 337/320 [75] Inventor: James W. Welsh, Summit, NJ.

[73] Assignee: Standard Motor Products, Inc.,

Long Island City, NY. Primary Examiner-Roy N. Envall, Jr. [22] Filed: Oct. 18, 1972 [21] Appl. No.: 298,523

' [57] ABSTRACT [52] US. Cl 337/320, 337/117, 337/318,

337 321,219 513, 73 368 [51] Int. Cl. H0lh 37/40 A caplnary Protector dlsclosed m whlch comamed 5 Field of Search 337 117 120 121 30 material, vaporizable at a temperature of interest, is

337/317 318 319 320 maintained in exclusively liquid state when the protec- 32'3, 327 6 tor is at a temperature below such preselected temper- 5 ature. Methods for using such capillary protector and heating apparatus incorporating the same are also dis- [56] References Cited closed' UNITED STATES PATENTS 3,284,600 11/1966 Mertler 337/318 9 Claims, 8 Drawing Figures PATENIED m 7 Ian- SHEET 2 0F 2 77 f/a FIG. 7

METHOD AND APPARATUS FOR HEAT DETECTION AND CONTROL FIELD OF THE INVENTION This invention pertains to method and apparatus for use in heat detection and control.

BACKGROUND OF THE INVENTION In various applications, such as the baseboard heating of buildings, refrigeration, fire detection in aircraft and the like, the capability for unattended monitoring of generated heat at its point of origin is of great importance. In the first-mentioned application, the possibility of danger to personnel and property upon the unnoticed collection of debris or the like upon baseboard units are matters of such concern as to have influenced baseboard unit manufacturers to provide heat detection apparatus spacedly disposed from and in common housings with such units.

One variety of heat detection apparatus in present use in baseboard units, and generally referred to as a capillary protector, comprises a tube containing a liquid vaporizable at the temperature of interest and expanding volumetrically to actuate a switch which in turn energizes an alarm or discontinues baseboard unit energization. Some capillary protectors are constructed to intentionally include, in such contained liquid, a void or gas bubble, which can be readily observed if the capillary protector contents are carefully withdrawn into a transparent tubular container. In operation of such void-type capillary protectors, upon the occurrence of transitions from liquid to vapor, which involve substantial volume expansions, the void increases in magnitude and a diaphragm in enclosing relation to the liquid is displaced sufficiently to operate electrical alarm or heating control switches.

Void-type capillary protectors are, by reason of such void, incapable of providing reliable indication of hotspots throughout their longitudinal extent. Thus, if in initially deploying a void-type capillary protector, one applies heat to a tube location containing the void thereof, the protector liquid does not vaporize sufficiently to effectuate volumetric expansion of magnitude operating the associated switch. By way of further example, if in the initial deployment of a void-type capillary protector, one applies heat to a tube location containing liquid, the liquid does vaporize and does change volumetric character sufficient for switch operation. However, the void travels to such tube location. Accordingly, on the next occurrence of heating at that same tube location, the associated switch is not operated since volumetric expansion is of insufficient magnitude.

The shortcomings of void-type capillary protectors are further evident from other practical considerations. First, the independent laboratories which pass safety judgement on capillary protectors for baseboard heaters presently require only that the protector operate its associated switch on the occurrence of a blockage (heat containment caused by an object disposed on the heater) of no less than one lineal foot. Void-type capillary protectors readily meet this limited requirement since such blockage is of extent much larger than their void extent. Secondly, in related refrigeration applications where hot-spots are of major concern, the industry has not found the capillary protector to be satisfactory but,rather, has turned to the use of a plurality of detectors disposed individually at the hot-spot loca tions of interest.

Capillary protectors of the type not containing a void in their liquid volume on initial construction also exhibit shortcomings rendering their use less than desirable. In these devices a void is necessarily formed upon liquid vaporization due to heating. However, as applicant has determined, upon the removal of such heating, theprocess is not completely reversible. Thus, while some vapor does return to liquid state upon such removal of heating, some vapor in fact remains. As the protector is subjected to repeated heat detecting operation, such residual vapor increases in volume and results ultimately in a substantial void in this originally voidless type of capillary protector. At this stage, the device is no more suitable for use than is the void-type capillary protector discussed heretofore.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved method for use in detecting each occurrence of a preselected temperature in any extent of an elongate path.

A further object of the invention is to provide an improved capillary protector for use in heat detection.

It is another object of the invention to provide improved baseboard heating apparatus.

A more particular object of the invention is to provide a capillary protector providing reliable heat detection on repetitive use and throughout all subdimensions of its lineal extent. v

In the efficient attainment of the foregoing and other objects, the present invention provides methods for detecting the occurrence of preselected temperatures in an elongate path by disposing a voidless capillary protector in the path and insuring that such protector con tainsmaterial in exclusively liquid state at all times during which the temperatures'in said path are below the preselected temperature. The invention further provides a capillary protector including therewithin means for maintaining the material thereof in exclusively liquid state during non-detecting or inactive periods. In the improved heating apparatus provided by the invention, the capillary protector of the invention is provided in integral assembly with a heating unit for controlling operation thereof.

The foregoing and other objects and features of the invention will be evident from the following detailed description thereof and from the drawings wherein like reference numerals are employed to designate like parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic drawing explanatory of the methods of the invention.

FIG. 2 is a front elevational view, partly in section, of a capillary protector constructed in accordance with the invention.

FIG. 3 is a side elevational view taken along the lines III-Ill of FIG. 2.

FIG. 4 is a front elevational view of heating apparatus constructed in accordance with the invention, partly broken away to show detail.

FIG. 5 is a side elevational view taken along the lines VV of FIG. 4. t

FIG. 6 is a sectional perspective view showing a resistance heating element employable in the heating apparatus of FIG. 4.

FIGS. 7 and 8 are respectively front and side elevational views of alternate switch structure for use in practicing the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, the methods of the invention all involve, at their outset, the provision of a heatconductive container 10 containing a material 12 in exclusively liquid form when the container is belowa preselected temperature of interest, the material being vaporizable at such temperature Material 12 preferably comprises silicon oil. In the illustrative manner of implementing the methods in FIG. 1, a displaceable floatation member 14 is next inserted into the upwardly extending section of container 10 into engagement with the liquid surface of material 12. Various procedures may now be adopted, if necessary, to insure that the material contained by floatation member 14 in tube 10 is in such exclusively liquid state, e.g., the container may be subjected to gas bleeding through member 14 or the container sidewall. Indicator 16 is connected to floatation member 14 and a graduated scale 18 is fixedly supported relative to container 10 and in cooperative relation with the indicator. By this arrangement, a measure (A) is obtained of the volume of the contained material in its exclusively liquid state. An extent of container 10 is now subjected to heating to the preselected temperature and the contained material accordingly vaporizes in part to form a void therein. Accompanying such heating, and, for simplification, omitting detailed discussion of volumetric expansion other than that directly due to vaporization of the contained material, floatation member 14 is displaced into its uppermost broken line position and indicator 16 provides indication of a measure (B) of the volumetric expansion of material 12 according withthe occurrence of the heating of such container 10 extent to the preselected temperature.

Upon the removal of the heating influence and the recession of container 10 temperature to below the preselected temperature, the void diminishes. As discussed heretofore, the void does not diminish totally,

i.e., certain vapor remains in the contained material. This condition is shown by the lower broken line showing of floatation member 14 and by the measure (C) indication, whereby it may be seen that the floatation member does not return to its original, solid line, position but is displaced slightly above such position, exaggerated in FIG. 1 for purposes ofillustration. In accordance with the methods of the invention, floatation member 14, and hence the contained material, is now subjected to a force, shown schematically as being applied by member 20, of magnitude sufficient to return the floatation member to its original position. Otherwise stated, the material is pressurized until it returns to its measured liquid state volume wherein the indicator registers with the scale at measure (A).

Following such procedure in the nature of calibration, tube. 10v is disposed in an elongate path in which occurrences of the preselected temperature are to be detected and a determination is made of each volumetric expansion of material 12 of predetermined measure (B) or greater and the material is subjected to pressure sufficient to cause it to return to its liquid state volume, measure (A), at least after each such volumetric expansion. In the manner of implementing the method in FIG. 1, the latter steps are practiced by detecting excursions of indicator l6 and by applying pressure through member 20 to floatation member 14. By this procedure, each occurrence of such preselected temperature in the path under study is detected.

The material pressurizing steps of the methods of the invention may be practiced on a continuing basis rather than following each occurrence of the preselected temperature in the path under study. For example, a spring 22 or other continuous force-producing member may be connected to tube 10 and to floatation member 14 for continually exerting sufficient force on floatation member 14 as to insure that the same will return to its original position after all displacements thereof due to container heating to the preselected temperature and thereabove.

Referring to FIG. 2, capillary protector 24 comprises a hollow heat-conductive tube 26 containing the foregoing material 12 in exclusively liquid state. Tube 26 is provided with a closure member including a resilient portion in engagement with the contained material. In FIG. 2, such closure member includes a diaphragm 28 and a housing 30, the diaphragm margins being disposed in abutting relation with both tube 26 and housing 30. An extendedmarginal portion of diaphragm 28 abuts with housing 30 and is thus not deformable outwardly of the tube. The remaining expanse of diaphragm 28 interiorly of this marginal portion is unrestrained and hence is readily deformable both outwardly and inwardly of tube 26. By appropriate dimensioning of the readily deformable interior expanse of diaphragm 28, the diaphragm is caused to exert a continuing pressure upon material 12 for purposes abovediscussed in connection with the methods of the invention, i.e., a force sufficient to maintain the material in exclusively liquid state when tube 26 is at temperatures below the preselected temperature of interest. Diaphragm 28 is preferably comprised of a synthetic plastic material such as polyimide film.

Housing 30 fixedly supports an electrical contact element 32 and a terminal 34 connected thereto. The housing supports a further electrical contact element 36 on movable support arm 38. Terminal-40 is provided with electrical continuity to movable contact element 36 by support arm 38 and a further support arm 42, arm 38 being pivotally supported by arm 42 at its point of juncture therewith. Displacement of support arm 38 is controlled by actuator 44, also supported for pivotal movement by support arm 42, by spring 46 whose extremeties are respectively contacted to support arm 38 and actuator 44 and by fail-safe linkage 48. Actuator 44 includes an arcuate portion 44a adapted for engagement with diaphragm 28. Housing 30 includes a recess 50 adapted to limit rightward movement of contact arm 38. The manner in which the apparatus of FIG. 2 implements the methods of the invention will now be discussed.

In its configuration shown in FIG. 2, diaphragm 28 is shown in engagement with material 12 under the conditions wherein tube 26-is effectively containing the material, i.e., has not been ruptured, wherein tube'26 is throughout its extent at a temperature below the preselected temperature and wherein material 12 is in exclusively liquid state. The illustrated configuration of diaphragm 28 provides a measure of the volume of material 12 under these conditions and contacts 32 and 36 are maintained in engagement by the diaphragm since the diaphragm exerts force on actuator 44 such that spring 46 forces support arm 38 into its illustrated position. On the occurrence of the heating of an expanse of tube 26 to the preselected temperature or above, material 12 vaporizes in part and the deformable expanse of diaphragm 28 is urged leftwardly to rotate actuator 44 counterclockwise. Upon such rotation of actuator 44, spring 46 passes through an equilibrium condition and thereupon, in snap-action, drives support arm 38 into recess 50, thereby disengaging contacts 32 and 36. Such deformation of diaphragm 28 provides a configuration thereof indicative of volumetric expansion of material 12 according with the occurrence of heating of tube 26 intended to be detected. This situation will persist until heat is removed from tube 26 and the void occasioned therein by the heating commences to diminish.

As such void is driven to nil by pressurization of material 12 by diaphragm 28, a reverse snap-action occurs under the influence of spring 46 and contacts 32 and 36 are reengaged. In the event that tube 26 is ruptured in use, or otherwise leaks material therefrom, diaphragm 28 will deform inwardly of tube 26 and will be followed by actuator portion 44a under the influence of spring 46. On this occurrence, fail-safe linkage 48, which is secured to actuator 44, engages arm 38 and disengages the reengaged contacts 32 and 36.

In usage of the apparatus of FIG. 2, one of terminals 34 and 40 is connected to a heating element and the other terminal is connected to one terminal of the power supply for such heating element. Electrical continuity between terminals 34 and 40 is provided exclusively where tube 26 is below the preselected temperature and is in material-containing condition. On each occurrence of the preselected temperature in the path in which tube 26 is disposed, electrical continuity between terminals 34 and 40 is interrupted and the heating unit is thereby deactivated. As will be appreciated, the apparatus is repetitively operative since the sensitive liquid material thereof is maintained void-free.

Referring to FIGS. 4 and 5, heating apparatus in accordance with the invention comprises a convoluted 7 support 52 upstanding on a base 54. The base is prefer ably formed of a piece of sheet metal, the margins of which are curled downwardly to define legs 56 and 58 and the center of which is creased to define a trough 60 for supporting heat-conductive tube 62 containing a material such as material 12 above. A layer 63 of heatinsulative material, such as Mylar is preferably disposed between tube 62 and trough 60 to facilitate the exchange of heat between support 52 and tube 62. Such layer 63 is desirably comprised of noise-absorbent heat-insulative material to reduce noise emanation from the heating apparatus. Tube 62 extends throughout base 54 and terminates at diaphragm 28. The diaphragm and housing are arranged as in FIG. 2.

Convoluted support 52 includes a pair of opposed heat-conductive sheet members 64 and 66 which are secured to each other throughout their length, preferably by striking out a portion of member 66 and securing such portions to member 64. Such securements, 68, are made throughout the expanse of support 52 as indicated in FIG. 5. As also shown in FIG. 5,'member 64 may be wider than member 66. The convoluted support is secured to base 54 at its minimae, e.g., by spot weldmg.

Heat-conductive members 64 and 66 sandwich therebetween an electrical insulated resistance heating assembly 70, which is coextensive in length therewith. A preferred form of this assembly is illustrated in FIG. 6 wherein a resistance wire 72, which may comprise an iron ribbon chromium aluminum alloy is enclosed by an electrically insulative thin film wrapping 74 ofa material such as polyimide film.

At the terminations of convoluted support 52, resistance wire 72 is led on the one hand to terminal 34 of housing 30, and on the other hand directly to one terminal of a power supply 76. The remaining terminal of the power supply is connected to terminal of housing 30.

The heating apparatus of FIG. 4 is energized upon the foregoing connection of resistance wire 72 and remains in energized condition until the occurrence of the preselected temperature at any point along trough 60. On such occurrence, the diaphragm 28 (FIG. 2) and associated switch means are operative to disconnect supply 76 from wire 72 at one terminal thereof, and on the recession of heat in trough 60 from the preselected temperature to renew interconnection between the supply and resistance wire 72.

Referring to the alternate switch embodiment of FIGS. 7 and 8, housing 77 fixedly supports an electrical contact element 78 and a terminal 80 connected thereto. The housing supports further an electrical contact arm 82. Terminal 84 is provided with electrical continuity to contact arm 82 by support arm 86, arm

82 being pivotally supported by arm 86 at its point of juncture therewith. Displacement of contact arm 82 is controlled by actuator 88, also supported for pivotal movement by support arm 86 and by spring 90.

Unlike spring 46 above, which was a coil spring looped about and freely movable relative to arm 38 and actuator 44 (FIG. 2), spring is in strip metal form including a planar section 90a rigidly secured by welding or the like to contact arm 82 and a folded section 90b extending to actuator 88 and securely engaging a rib 88a thereof. Actuator 88 includes an arcuate portion 88b adapted for engagement with a diaphragm or other switch controller. Housing 76 includes a post 92 adapted to limit rightward movement of contact arm 82.

In the illustrated configuration thereof, the switch contact elements are disengaged, actuator 88 being in its furthest clockwise disposition abutting stops 86b of support arm 86. In the switch embodiment of FIG. 2, the separation of contact elements with the actuator so disposed was effected by fail-safe link 48 and, in the absence of such link, the contact elements would have been engaged under the influence of coil spring 46. In the FIG. 7 switch embodiment, contact separation with actuator 88 in its furthest clockwise position is effected by spring 90 which, by reason of its disposition and non-rotative securement to contact arm 82 and its gripping securement with rib 88a, lifts contact arm 82 away from contact element 78.

When a diaphragm or other member is placed in operative engagement with actuator portion 88b to rotate the actuator clockwise, the contacts are engaged. Snapaction disengagement and reengagement occur thereafter on actuator movement as discussed in the case of the FIG. 2 switch embodiment. Upon diaphragm or like failure, the switch assumes its illustrated configuration.

As will be appreciated, various parameters in the disclosed method control the time period which may occur between diaphragm deformation indicative of volumetric expansion of preselected extent and the return of the contained vaporizable material to exclusively liquid state. Accordingly, the material and the magnitude of pressurization thereof, e.g., by diaphragm 28, are selected in conjunction with apparatus dimensions to satisfy the desired time period.

Various changes and modifications in the method and apparatus of the invention will be evident to those skilled in the art. Accordingly, the foregoing disclosed particular embodiments of the invention are intended in an illustrative and not in a limiting sense. The true spirit and scope of the invention is defined in the following claims.

What is claimed is:

1. Apparatus for use in detecting the occurrence of a preselected temperature in an elongate path comprismg:

a. a hollow heat-conductive tube having a closed end and an open end and filled with material in exclusively liquid state, said material vaporizing at said preselected temperature; b. a closure member for said open tube end, said closure member having a resilient portion in engagement with said material, said closure member resilient portion being supported for deformation outwardly of said tube upon partial vaporization of said material, said closure member applying pressure to said material of a magnitude sufficient for maintaining said material in exclusively liquid state when said tube is at a temperature below said preselected temperature, said closure member resilient portion being further supported for deformation inwardly of said tube upon leakage of said material from said tube; and

c. switch means having an actuator in operative engagement with said closure member resilient portion, a pair of normally-engaged contacts, and spring means connecting said actuator to at least one of said contacts, said actuator disengaging said contacts upon each occurrence of predetermined deformations of said closure member resilient portion outwardly and inwardly of said tube.

2. The apparatus claimed in claim 1 wherein said switch means provides for snap action disengagement of said contacts on each occurrence of said predetermined deformations of said closure member resilient portion outwardly of said tube.

3. The apparatus claimed in claim 1 further including a housing supporting said switch means, said closure member comprising a diaphragm having a marginal ex- 8 panse in abutting relation with said housing, .the expanse of said diaphragm interiorly of said marginal expanse constituting said closure member resilient portion.

4. Apparatus for use indetecting the occurrence of a preselected temperature in an elongate path comprismg: g

a. a hollow heat-conductive tube having a closed end and an open end and filled with material in exclusively liquid state, said material vaporizing at said preselected temperature; I b. a closure member for said open tube end, said closure member having a resilient portion in engagement with said material, said closure member resilient portion being supported for deformation outwardly of said tube upon partial vaporization of said material, said closure member applying pressure to said material of a'magn'itude sufficient for maintaining said material-is exclusively liquid state when said tube is at a temperature below said preselected temperature;

c. switch means having an actuator in operative engagement with said closure member resilient portion;

. an electric heater having a passage therein defining said elongate path and containing said tube, said heater including a heat-generating conductor; and

e. means connecting said conductor to said switch means.

5. The apparatus claimed in claim 4 whereinsaid heater further comprises a base containing said passage, electrically insulative means enclosingsaid conductor and heat-conductive means secured to said base and enclosing said insulative means.

6. The apparatus claimed in claim 5 wherein said conductor, said insulative means and said heatconductive means are of like length substantially greater than the length of said base, and together comprise a convoluted assembly having a length equal to that of said base, longitudinally spaced parts of said heat-conductive means being secured to said base.

7. The apparatus claimed in claim 4 wherein said electric heater includes a heat-insulative member partially encircling said tube and disposed in said passage.

8. The apparatus claimed in claim 4 wherein said electric heater includes a noise-absorbent member partially encircling said tube and disposed in said passage.

9. The apparatus claimed in claim 4 wherein said electric heater includes a heat-insulative noise absorbent member partially encircling said tube and disposed in said passage. 

1. Apparatus for use in detecting the occurrence of a preselected temperature in an elongate path comprising: a. a hollow heat-conductive tube having a closed end and an open end and filled with material in exclusively liquid state, said material vaporizing at said preselected temperature; b. a closure member for said open tube end, said closure member having a resilient portion in engagement with said material, said closure member resilient portion being supported for deformation outwardly of said tube upon partial vaporization of said material, said closure member applying pressure to said material of a magnitude sufficient for maintaining said material in exclusively liquid state when said tube is at a temperature below said preselected temperature, said closure member resilient portion being further supported for deformation inwardly of said tube upon leakage of said material from said tube; and c. switch means having an actuator in operative engagement with said closure member resilient portion, a pair of normallyengaged contacts, and spring means connecting said actuator to at least one of said contacts, said actuator disengaging said contacts upon each occurrence of predetermined deformations of said closure member resilient portion outwardly and inwardly of said tube.
 2. The apparatus claimed in claim 1 wherein said switch means provides for snap action disengagement of said contacts on each occurrence of said predetermined deformations of said closure member resilient portion outwardly of said tube.
 3. The apparatus claimed in claim 1 further including a housing supporting said switch means, said closure member comprising a diaphragm having a marginal expanse in abutting relation with said housing, the expanse of said diaphragm interiorly of said marginal expanse constituting said closure member resilient portion.
 4. Apparatus for use in detecting the occurrence of a preselected temperature in an elongate path comprising: a. a hollow heat-conductive tube having a closed end and an open end and filled with material in exclusively liquid state, said material vaporizing at said preselected temperature; b. a closure member for said open tube end, said closure member having a resilient portion in engagement with said material, said closure member resilient portion being supported for deformation outwardly of said tube upon partial vaporization of said material, said closure member applying pressure to said material of a magnitude sufficient for maintaining said material is exclusively liquid state when said tube is at a temperature below said preselected temperature; c. switch means having an actuator in operative engagement with said closure member resilient portion; d. an electric heater having a passage therein defining said elongate path and containing said tube, said heater including a heat-generating conductor; and e. means connecting said conductor to said switch means.
 5. The apparatus claimed in claim 4 wherein said heater further comprises a base containing said passage, electrically insulative means enclosing said conductor and heat-conductive means secured to said base and enclosing said insulative means.
 6. The apparatus claimed in claim 5 wherein said conductor, said insulative means and said heat-conductive means are of like length substantially greater than the length of said base, and together comprise a convoluted assembly having a length equal to that of said base, longitudinally spaced parts of said heat-conductive means being secured to said base.
 7. The apparatus claimed in claim 4 wherein said electric heater includes a heat-insulative member partially encircling said tube and disposed in said passage.
 8. The apparatus claimed in claim 4 wherein said electric heater includes a noise-absorbent member partially encircling said tube and disposed in said passage.
 9. The apparatus claimed in claim 4 wherein said electric heater includes a heat-insulative noise-absorbent member partially encircling said tube and disposed in said passage. 